Protein crystallography continues to play an important role in the advances of biochemical research. This application proposes that our current unreliable instrumentation be updated to 21st century standards. This is not only important for the Medical College of Wisconsin, but for the entire southeastern Wisconsin region, since this is the only facility in this region for performing X-ray crystallographic experiments on biological macromolecules. The majority of the direct participants in this shared instrumentation come from the department of Biochemistry, although there is some participation from the department of Microbiology and the University of Wisconsin at Milwaukee. On going projects that will benefit from continued X-ray diffraction here at the Medical College include: (1) Structure and Function of a Flavoprotein Dehydrogenase, (2) Structure and Mechanism of a FMN and FAD-containing Enzymes, (3) Mevalonate metabolizing enzymes, (4) Structural Analysis of the Mannose 6- Phosphate Receptors, (5) Sorting of the IGF-II Receptor in Polarized Cells, (6) ATP-, Ubiquitin-dependent proteolysis, (7) Function of an interferon-induced ubiquitin homolog, (8) 4-Hydroxyphenylpyruvate Dioxygenase and Tyosinemia-1, (9) Design & Synthesis of Inhibitors of Human NOS Isoforms, (10) Design & Synthesis of Inhibitors of a-Glutamylcysteine Synthetase, (11) Roles for the divergent structural species of human lymphotactin, (12) Structure and Function of ExoS and related proteins, (13) Unique amino domains and AMP deaminase isoform diversity, (14) Proteases and Corneal Ulceration, (15) Maspin in the Cornea, (16) Structure and Function of Methylglyoxal Synthase, (17) Specific inhibitors for a non-specific enzyme: Aldose Reductase, and (18) Structure and Function of Phosphoribulokinase.